1. Technical Field
The present invention generally relates to a post-treated sulfurized salt of an alkyl-substituted hydroxyaromatic composition. The present invention further relates to a post-treated sulfurized salt of an alkyl-substituted hydroxyaromatic composition having a reduced content of unsulfurized alkyl-substituted hydroxyaromatic compound and its unsulfurized metal salt, methods of making same and their use in lubricating oil compositions.
2. Description of the Related Art
The lubricant additive industry generally uses alkyl phenols (e.g., tetrapropenyl phenol, TPP) to prepare detergents comprising sulfurized metal alkyl phenate. Metal salts of sulfurized alkylphenols are useful lubricating oil additives which impart detergency and dispersancy properties to the lubricating oil composition for marine, automotive, railroad and air-cooled engines as well as providing for an alkalinity reserve in the oil. Alkalinity reserve is necessary in order to neutralize acids generated during engine operation. Without this alkalinity reserve, the acids so generated would result in harmful engine corrosion. However, there may be some unreacted alkyl phenols such as tetrapropenyl phenol present in the sulfurized metal alkyl phenate as well as in lubricating oils containing one or more of the sulfurized metal alkyl phenates.
A recent reproductive toxicity study in rats sponsored by the Petroleum Additives Panel of the American Chemistry Council shows that free or unreacted TPP may cause adverse effects on male and female reproductive organs. Further, it is believed that TPP may be corrosive or irritating to the skin.
U.S. Patent Application Publication No. 20080070818 (“the '818 publication”) discloses a lubricating oil composition including at least one sulphurized overbased metal phenate detergent prepared from a C9-C15 alkyl phenol, at least one sulphurizing agent, at least one metal and at least one overbasing agent; the detergent including less than 6.0% by combined mass of unsulphurized C9-C15 alkyl phenol and unsulphurized metal salts thereof. Examples A and B disclosed in the '818 publication obtained an overbased detergent having 5.58 and 3.84 mass %, respectively, of unsulphurized alkyl phenol and its unsulphurized calcium salt.
U.S. Patent Application Publication No. 20090143264 (“the '264 publication”) discloses sulfurized metal alkyl phenate compositions having a low alkyl phenol content. The sulfurized metal alkyl phenate compositions of the '264 publication can be prepared by reacting a phenol compound such as tetrapropenyl phenol with an aldehyde to form a phenolic resin and then reacting the phenolic resin simultaneously with a metal base and a first sulfurizing agent.
U.S. Pat. No. 3,649,229 (“the '229 patent”) discloses a condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound, wherein the alkyl group has a molecular weight from about 600 to about 3,000; (2) an amine which contains a HN< group, i.e., an active hydrogen, and (3) an aldehyde, wherein the respective molar ratio of the reactants is 1:0.1-10:0.1-10. Example 7 of die '229 patent discloses that Mannich reaction of polypropylphenol sulfide with diethylenetriamine and paraformaldehyde.
U.S. Pat. No. 4,088,586 (“the '586 patent”) discloses a Mannich base prepared by condensing tetrapropenylphenol, formaldehyde and diethylenetriamine. The '586 patent further discloses that the calcium salt of the Mannich base is prepared using conventional methods, for example, by treating the Mannich base with calcium hydroxide in the presence of a promoter.
U.S. Pat. No. 4,157,308 discloses Mannich bases and the alkaline earth metal salts thereof which are prepared by condensing formaldehyde and a polyamine with a phenolic mix tore consisting of (1) from 95 to 30% phenol alkylated with a propylene tetramer and (2) from 5 to 70% phenol alkylated with a straight-chain alpha-olefin of from 16 to about 28 carbon atoms or alpha-olefin mixtures wherein the alpha-olefins are of from 16 to about 28 carbon atoms.
U.S. Pat. No. 4,157,309 discloses Mannich bases and the alkaline earth metal salts thereof, which are prepared by condensing formaldehyde and a polyamine with a sulfur-containing phenolic mixture consisting of (1) from 5 to 35 mol percent of a sulfurized alkylphenol wherein the alkyl group is C8-C36 alkyl, and (2) from 95 to 65 mol percent of phenol alkylated with a propylene tetramer.
U.S. Pat. No. 4,175,044 discloses Mannich bases and the alkaline earth metal salts thereof, which are prepared by condensing formaldehyde and a polyamine with a sulfur-containing phenolic mixture consisting of (1) from 5 to 40% of a sulfurized alkylphenol wherein the alkyl group is C8-C36 alkyl, and (2) from 95 to 60% of a phenolic mixture consisting of (a) from 95 to 30% phenol alkylated with a propylene tetramer and (b) from 5 to 70% phenol alkylated with a straight-chain alpha-olefin of from 16 to about 28 carbon atoms or alpha-olefin mixtures wherein the alpha-olefins are of from 16 to about 28 carbon atoms.
GB1604609 discloses in Examples G and 2 the condensation product of a mixture of alkyl phenol and a carbonated and non carbonated sulfurized alkylphenol/salt mixture, diethylamide triamine, and paraformaldehyde.
However, problems associated with the use of a polyamine in preparing a Mannich reaction product includes formation of sediment and plugging issues due to the multiple reactions occurring from the highly reactive polyamine, as well as being too viscous a material.
To reduce any potential health risks to customers and to avoid potential regulatory issues, there is a need to reduce the amount of free unsulfurized alkyl-substituted hydroxyaromatic compound and its metal salt in the salts of sulfurized alkyl-substituted hydroxyaromatic compositions. Accordingly, it is desirable to provide an improved process for making post-treated salts of sulfurized alkyl-substituted hydroxyaromatic compositions which have relatively low levels of unsulfurized alkyl-substituted hydroxyaromatic compound and its metal salt.